The mental gymnastics Witnesses go through on this topic is of gold medal Olympic proportions. When such events happen and the Witnesses seem to be miraculously saved the response is - "Praise Jehovah! Faithfully remaining loyal to Jehovah and his organization will literally save your life." When such tragedies happen and the outcome is not so nice the response comes in one of two forms -
"It is as the Bible says, 'Time and unforeseen circumstances,'" or
"They must have had a 'secret sin' that caused Jehovah to remove his protection."
So, the question to present in the 2 tragedies listed in the original post is this - Which was it? Did 2 JW couples who moved to a foreign nation because "the need was great" end up raped, tortured, and murdered because of dumb luck or did they have a secret sin? Did 43 Witnesses drowned to death after being swept out to sea because of dumb luck or were all 43 committing a secret sin that caused Jehovah to remove his protection?
A Witness might respond "Sometimes Jehovah protects his faithful people because they yet still have some purpose to fulfill got him." To which I would respond, "Do you mean the same God who has 8 million servants worldwide, but who would use rocks to cry out if no one proclaimed his holy name?"
In short, the Watchtower's own teaching in writing states that those 2 couples had to be allowed to be tortured, raped, and murdered to prove that humankind needs God and to prove Satan's claim that humans do not need God a lie. 43 Witnesses who agree with that statement had their lives cut short by drowning at see to prove that same point.